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Terms in this set (439)

• Several findings challenge the dopamine hypothesis
1) Antipsychotics block dopamine receptors right away, yet drug treatment takes ~2 weeks to reach full effect
- If schizophrenia is merely an increase in dopamine, drugs should work right away
- **More recent research suggests that the drugs may reduce psychotic symptoms relatively quickly, but it takes time for treatments to reach full effect. (measured by surveys like: are you still experiencing hallucinations? how intense are they? etc)
2) Not all schizophrenic patients respond to drugs that block dopamine receptors
- If schizophrenia is merely an increase in dopamine, drugs should work for all patients
3) Dopamine blockers can alleviate psychosis, but do
not treat negative symptoms
- If cognitive deficits are due to an increase in dopamine, these drugs should alleviate the symptoms
4) Some drugs that reduce symptoms do not block D2 receptors that well
• Example: Clozapine (atypical
antipsychotic)
• Not as effective at blocking D2 receptors as classical antipsychotics
- Less likely to produce motor side effects
• Has a much higher affinity to other receptors, like serotonin (5 HT)
• Can improve negative symptoms (possibly via 5 HT blockade)
- If positive and negative symptoms are merely due to overstimulation of D2
receptors, atypical antipsychotics shouldn't work as well
• Treatment issue: some patients have an adverse blood reaction to clozapine; not all patients can take it safely
-Racloprode= typical antipsychotic, it is very "Sticky" to the D2 receptors
-Clozapine= atypical antipsychotic, less "sticky" to D2 receptors, binds more to seratonin receptors. Sometimes have benefits for the negative symtoms and cognitive defecits
-atypical psychotics typically make the patient gain a lot of weight and can affect hormone levels in males and make them grow breasts
5) Drugs that increase dopamine release can improve negative symptoms
• Study: Schizophrenics and controls tested on a working memory task (dependent on PFC function)
• Given either placebo or low dose of amphetamine (a dose that increases dopamine release, but not psychotic symptoms)
— Note: higher doses of amphetamine do exacerbate symptoms
• Under placebo, schizophrenics performed
worse than controls
• Amphetamine, improved performance in
schizophrenics, up to control levels
-If schizophrenia is just an increase in dopamine, then why should a drug that increases dopamine release improve cognitive functions?